Driving rack mechanism



g- 5, 1952 P. H. KARLSSON EI'AL 2,605,646

DRIVING RACK MECHANISM Filed Sept. 1, 1948 Patented Aug. 5, 1952 unlrsoi smras '1 Claim. 1

The present invention relates to heat exchange apparatus and particularly to an improveddriv ing means for the rotor of a rotary regenerative air preheater or the like.

A conventional regenerative air preheater of the Ljungstrom type includes a rotor carrying heat absorbing surface in the form of metallic plates that are first positioned in a gas passage to absorb heat and then upon turning of the rotor become disposed in the air passage to impart heat to air flowing therethrough. Although a majority of air preheaters have a central drive utilizing a motor and gear reduction connected directly to the rotor posts, some rotors are provided with a driving rack extending circumieren-l tially of the outer cylindrical wall of the rotor.

high temperature gases and this sometimes reo. .7 3,665,646 I. I I 1 DRIVING nAoKf EoimNis Per Hilmer' Karlsson, Wellsviile, and" John 'A;: 1 1

Lidford, Friendship, N, Y as'signors to The Preheater Corporation, New YDIk,N, Y. y Application September 1,1948, swimw ar- Air-Q. 3

As the rotor structure turns it is subjected to sults in excessive distortion of the driving rack due to temperature variations of the rotor causing expansion of the latter. Inasmuch as the motor driven pinion that engages the rack for turning the rotor is mounted in a fixed position with respect to the rotor the distortion of the rack causes binding between it and the driving pinion with excessive wear of both among other disadvantageous conditions.

An object of the present invention is to obviate the above mentioned disadvantages by providing what may be termed as semi-flexible; mounting 'for the drive rack. The invention will be best understood upon consideration of the following detailed description of an illustrative embodiment thereof when read in conjunction with the accompanying drawing in which:

Figure l is a schematic elevational view of the lower half of an air preheater rotor turning on a horizontal axis and utilizing a mounting for the drive rack embodying the present invention. Figure 2 is a fragmentary perspective view on an enlarged scale illustrating the mounting for the drive rack shown in Figure 1; and t Figure 3 is a similar perspective view of a modified type of mounting for the drive rack.

In the drawings the numeral Iii designates the cylindrical shell of a rotor which. is divided into sector shaped compartments H by radial partitions l2 connecting it with the rotor post l3. The rotor compartments H'contain regenerative heat transfer material in the form of metallic plates which are spaced apart to form passages parallel to the rotor axis. The plates first absorb heat from hot gases flowing through the gas passage of the preheater and as the rotor turns slowly about its axis the heated plates are moved into a stream of air flowing through the air passage, the heated air being eventually conveyed to a boiler furnace or further place of use. For the purpose of turning the rotor about its axis a pinion l5 driven by a motor I! through reduction gearing 18 engages a tooth rack desig- -22 held inplace in the bars by cotter pins 24.

Such constructions are conventional and are known as pin racks. 1

However, in accordance with the present invention the drive rack it which is made up of a plurality of segmental sections welded together at 25 where they abut to form a complete circular ring and the ring is attached to the rotor shell I!) by means of a plurality of circumferentially spaced mounting blocks 26 located between the shell I8 and rack l6 and fixed to both of these parts, as by welding. The mounting blocks 26 not only space the drive rack l6 outwardly of the rotor shell It but in accordance with the invention they are located circumferentially at points that are not in alinement with, or opposite, the ends of any of the radial partitions [2 that divide the interior of the rotor to form the compartments II. The mounting blocks 26 may be located half way between the radial partitions. Excessive distortion of the rack due to temperature variation of the rotor structure is avoided because the partitions l2 do not exert a thrust on the drive rack 16 and the shell plate [0 of the rotor acts more or less as a diaphragm to provide a semi-flexible mounting for the pin rack.

In the form shown in Figure 3 the rack bars 20, 21 are provided with mounting studs 30 that extend into elongated slots 32 in mounting brackets 33 mounted above and below the rack bars 29, 2!, respectively, and attached to the rotor shell ill as by welding. With this form also expansion of the rotor upon being heated may take place without distorting the drive rack (6 since the pins 3!] may move radially in the slots 32 of the brackets 33.

With both forms of rack mounting described above the rotor structure may expand without producing a corresponding movement of the drive rack which would distort it and consequently the driving relation between the driving rack l6 and pinion I5 is maintained without binding and excessive wear of these parts is eliminated.

What we claim is:

[In apparatus having a, rotor comprising a cylindrical shell :made of a metal that flexes under stress connected by radially extending members to a rotor post and subjected to distorand an annular driving rack extending nircume ferentially of the rotor and having a diameter somewhat greater than thatof the latter so :asdzo be spaced radially therefrom; means attaching. said driving rack to the rotor consisting of mounting blocks attached toethe rotor and :to the rack in the space therebetween at points that are spaced circumferentially of the rotor and located only in the intervals between and out of alinement with said radial members so that the expansion of said members causes said shell to flex in areas between said blocks.

PER HILIWER KARLSSON. JOHN A. LIDFORD.

REFERENCES CITED I I I The followin references are of record in the tion due to unequal heating of portions thereof, g

file of this patent:

V :UNITED STATES PATENTS Number Name Date '.'77B,.16-2j Anderson Oct. 25, 1904 1,231,4283 Aldrich Aug. 21, 1917 2,313,081 Ljungstrom Mar. 9, 1943 144L901 Petersen May 18, 1948 

